1. Field of the Invention
The present invention relates to a process and plant for building tyres for vehicle wheels.
In particular, the present invention relates to a method for managing a carcass structure building line for tyres of vehicle wheels, and a process and plant for building tyres for vehicle wheels for carrying out such a method.
2. Description of the Related Art
Tyre production cycles provide that, after a building process in which the various structural components of the tyre itself are made and/or assembled in one or more building lines, a moulding and vulcanization process, suitable for defining the tyre structure according a desired geometry and tread pattern, is carried out in a suitable vulcanization line.
A tyre for vehicle wheels typically comprises a carcass structure, shaped according to a substantially toroidal configuration, comprising at least one carcass ply having respectively opposite end portions. The latter are engaged with respective anchoring annular structures, generally called “bead cores”. The anchoring annular structures are arranged in regions usually identified with the term “beads”. The beads have an inner diameter substantially corresponding to a so-called “fitting diameter” of the tyre on a respective mounting rim. The tyre also comprises a crown structure comprising at least one belt strip arranged in a radially outer position to the carcass ply with reference to the centre of the tyre and a tread band in a radially outer position to the belt strip. Typically, on the tread band, longitudinal and transverse grooves are formed, arranged so as to define a desired tread pattern. Between the tread band and the belt strip(s) a so-called “underlayer” of elastomeric material can be interposed, having features suitable for ensuring a stable connection of the belt strip(s) with the tread band itself. The tyre further comprises a pair of so-called sidewalls of elastomeric material applied on opposite sides onto the lateral surfaces of the carcass structure. In tyres of the “tubeless” type, a layer of elastomeric material, usually called “liner”, having air-tightness features and extending from one bead to the other, is present in a radially inner position relative to the carcass ply.
By “elastomeric material” it is meant a composition comprising at least one elastomeric polymer and at least one reinforcing filler. Preferably, such composition further comprises additives, such as a cross-linking agent and/or a plasticizer. Thanks to the presence of the cross-linking agent, such material may be cross-linked by heating, so as to form the final manufactured article.
By “structural component” of the tyre it is meant any part of the tyre, or portion thereof, suitable for carrying out a function. Therefore, structural component are, for example: liner, under-liner, anti-abrasion inserts, bead core, fillers in the bead region, carcass ply/plies, belt strip(s), belt under-layer, tread band under-layer, sidewalls, sidewall inserts, tread band, textile or metallic reinforcements, reinforcing elements made of elastomeric material, etc.
By “stable association” or “stably associated” it is meant an association that lasts during the various steps of a tyre building process.
By “stable coupling” or “stably coupled” it is meant a coupling that lasts during the various steps of a tyre building process.
WO 2008/099236 to the same Applicant describes an apparatus for building tyres comprising a forming drum and auxiliary support elements. The auxiliary support elements are moved close to the forming drum for facilitating supply steps of elementary components in axially outer regions of the forming drum. After the carcass ply has been formed, the auxiliary support elements are moved away from the forming drum so as to be able to carry out a flap formation step wherein the ends of the carcass ply are folded so as to form flaps that contain the anchoring annular structures.
WO 2011/018687 to the same Applicant describes a plant for building tyres for vehicle wheels, comprising a carcass structure building line, which in turn comprises:                at least one forming drum;        at least one pair of support rings removably associable with the forming drum;        at least one support rings associating station including at least one device for associating the pair of support rings to the forming drum;        at least one support rings removing station including at least one device for removing the pair of support rings from the forming drum;        a first transfer device suitable for transferring the forming drum dissociated from the pair of support rings from the support rings removing station to a work station of the carcass structure building line;        a second transfer device suitable for transferring the pair of support rings dissociated form the forming drum to a support rings temporary storage.        
The Applicant has verified that, in the carcass structure building line of the type described by WO 2011/018687, employing forming drums and auxiliary support rings or elements, managing the transfers of the forming drums and of the support elements together with managing the association/removal of the support elements with/from the respective forming drum may be complicated, can make the building times longer, can require a significant amount of resources and can increase the sizes of the carcass structure building line.
In particular, the Applicant notes the such drawbacks may be proportionally more relevant when building processes are adopted which employ semifinished products made in advance and stored in respective storages.
In this case the Applicant observes that, being possible to make more compact building plants, the management of the support elements could considerably affect the plant layout, production and flexibility.